As I got older, I began to understand that money really is a
language the same way that Spanish is a language. And people who
learn how to be fluent in money have an advantage. A lot of
people don't think of money in those terms. They think of it as a
thing in and of itself, that money is this tangible thing called
dollars, but that's not right.

A dollar is essentially a fungible stand-in for some other type
of resource. Time is a resource. Energy is resource. A pension is
a resource. Once you understand that a dollar is just stand-in
for some other type of resource because we're trying to find some
easy way to exchange one resource for another, then you begin to
understand how money works.

He goes on to explain that some of the most meaningful questions
we ask ourselves are questions of money and value — not "Which
costs more?" but "What's worth more to me?"

He tells Wealthsimple:

If you think about it, many of the questions we spend the
most time thinking about are arbitrage questions: Does it make
more sense for you to go to work and hire a nanny or to stay home
with your kids? Should you catch up on your emails or spend half
an hour talking to your wife? What has more value to you?

At the root of that is actually one of the most important
questions about what it means to be human—we're constantly trying
to arbitrage to maximize those things that are meaningful and
minimize those things that aren't. That’s at the root of all
economic activity.

Duhigg's explanation provides another perspective on a common
piece of advice:
Money doesn't buy happiness. (Admittedly,
some people disagree.) By Duhigg's reasoning, that might be
partly because dollars can't buy the answers to questions of
value and time. If you can't place a price on time spent sifting
through your inbox or talking with your spouse, it hardly matters
how much you have.